Presently, integrated circuits are widely used in various electronic products such as mobile phones, personal digital assistants, and liquid crystal displays. These kinds of electronic products usually need a lot of components to be electrically connected together. For example, in an LCD, the components can include integrated circuits (ICs), glass substrates, flexible printed circuits (FPCs), and printed circuit boards (PCBs), which are packaged together in the form of a module bonding structure. Generally, module bonding technologies for LCDs include chip on glass (COG) technology, tape automated bonding (TAB) technology, film on glass (FOG) technology, chip on board (COB) technology, and chip on film (COF) technology. A conductive bonding material for bonding two electronic components together, such as an anisotropic conductive film (ACF), is usually needed.
Referring to FIG. 5, a typical module bonding structure 10 includes a first IC 11, a second IC 12, an FPC 13, and a glass substrate 14. The first IC 11 is bonded on the glass substrate 14 by COG technology. The second IC 12 is bonded on an end of the FPC 13 by COF technology. The other end of the FPC 13 is bonded on the glass substrate 14 by COG technology.
Referring also to FIG. 6, this is essentially an abbreviated circuit diagram of the module bonding structure 10. The glass substrate 14 includes a plurality of conductive lines (not shown) therein. The FPC 13 includes a plurality of metal wires (not shown). The first IC 11 includes a plurality of first pins A1˜An (n is a natural number). The second IC 12 includes a plurality of second pins B1˜Bn. The first pins A1˜An correspond to the second pins B1˜B2 one-to-one. The first pins A1˜An are electrically connected to the corresponding second pins B1˜Bn via the conductive lines of the glass substrate 14 and the metal wires of the FPC 13, respectively. Normally, a bonding resistance inevitably exists in a bonding area because of a resistance of the bonding material and the ICs. Taking the first pin A1 and the second pin B1 as an example, R1 is a resistance between the first pin A1 and the glass substrate 14, R2 is a combined resistance of the metal wire of the glass substrate 14 corresponding to the first pin A1 plus the conductive line of the FPC 13 corresponding to the second pin B1, and R3 is a resistance between the FPC 13 and the second pin B1. Thus, a bonding resistance R between the first pin A1 and the second pin B1 is equal to the sum of R1, R2 and R3.
In general, the bonding resistance R has a maximum tolerance value, in order to meet requirements of stable and reliable operation when the module bonding structure 10 is used in an electronic product such as an LCD. However, during the process of manufacturing the module bonding structure 10, it is difficult to keep the bonding resistance R in a normal range below the maximum tolerance value. If the maximum tolerance value is exceeded, working signals of the module bonding structure 10 are liable to be adversely affected, and the module bonding structure 10 may not work accurately and stably.
What is needed, therefore, is a method for examining bonding resistance that can help overcome the above-described deficiencies.